1. Field of the Invention
The present invention relates to a hose having a connecting portion and a process for producing the same. The connecting portion is constructed so that a pipe and the hose are connected integrally with a resin coating portion. The present invention is applicable to a branched hose such as an automotive radiator hose or the like.
2. Description of the Related Art
There has been a connecting construction for a hose which is disclosed in U.S. Pat. No. 5,033,775, for instance. As illustrated in FIG. 16, this conventional hose connecting construction includes a branched pipe 100 branched in three directions, hoses 201, 202 and 203 disposed around each of the branched sleeves of the branched pipe 100, and a resin coating portion 300 covering the connecting portions between the hoses 201, 202 and 203 and the branched pipes 100.
In order to build the conventional hose connecting construction, the branched sleeves of the branched pipe 100 are inserted into the hoses 201, 202 and 203 respectively. Thereafter, the branched pipe 100 with the hoses 201, 202 and 203 installed (hereinafter simply referred to as an "insert assembly") is disposed in a mold 400 as illustrated in FIG. 17, and the outer peripheral surfaces of the hoses 201, 202 and 203 are pressed and sealed with sealing rings 401, 402 and 403 at the ends of the branched sleeves of the branched pipe 100, thereby fixing the insert assembly. Then, a molten resin is filled in a cavity 500, which is formed by the molding surface of the mold 400, the sealing rings 401, 402 and 403 and the insert assembly by injection molding, and thereby a resin coating portion 300 is molded around the connecting portions and the central portion of the branched pipe 100. During the injection molding, the resin coating portion 300 is solidified and shrunk by a molding shrinkage ratio of 0.5% or more, and accordingly each of the hoses 201, 202 and 203 is subjected to an injection molding pressure as well as a force reducing their diameters. As a result, the hoses 201, 202 and 203 are held firmly between the resin coating portion 300 and the branched pipe 100, and accordingly a high sealing pressure can be exerted between the hoses 201, 202 and 203 and the branched pipe 100.
However, in the conventional production process described so far, the hoses 201, 202 and 203 (i.e., resilient bodies) are held and retained with the sealing rings 401, 02 and 03. Consequently, there arises a phenomenon that the insert assembly disposed in the mold 400 is moved slightly over a distance of about 0.8 mm by the injection molding pressure during the injection molding. When the insert assembly is thusly moved, the thickness of the molded resin coating portion 300 is likely to become uneven, and flashes occur on the resin coating portion 300. In order to avoid these drawbacks, it is necessary to retain the insert assembly in the mold 400 with a much firmer retaining force.
Here, Japanese Unexamined Patent Publication (KOKAI) No. 241,595/1985 also discloses a method for retaining the insert assembly in the mold. In the method, a tab protruding from a surface of the branched pipe is disposed on the surface of the branched pipe, and it is brought into contact with a molding surface of the mold, whereby retaining the insert assembly in the mold. By using the method, it is possible to securely inhibit the insert assembly from moving. However, it becomes hard to cover the end surface of the tab with the resin coating portion, and accordingly there arises anxiety that the sealing property between the hoses and the branched pipe is liable to be dissatisfactory.
Further, in the aforementioned conventional production process, when the dimensions of the hoses 201, 202 and 203 or the like are changed, the capacity of the cavity 500 should be varied accordingly. Namely, when the molding material is injected in a greater amount, the molding material leaks between the sealing rings 401, 402 and 403 and the hoses 202 and 203, and thereby flashes occur on the resin coating portion 300. On the other hand, when the molding material is injected in a lesser amount, the molding material fails to fill the cavity 500 of the mold 400 completely (hereinafter simply referred to "short shot failures"). Therefore, it is necessary to precisely determine the optimum injection amounts whenever the dimensions of the hoses 201, 202 and 203 or the like are changed. As a result, in the aforementioned conventional production process, the man-hour requirement tends to increase, and accordingly the productivity tends to deteriorate.